(1) Field of the Invention
The present invention relates to a removable fastener device equipped with attachment means for attaching an external load and with fastener means for fastening said attachment means to an aircraft, and also relates to an aircraft equipped with such a device and to an associated method.
The technical field of the invention is thus the field of fastener devices for fastening an external load to an aircraft, and in particular to a rotary-wing aircraft.
(2) Description of Related Art
Conventionally, an aircraft has a structure, referred to by convenience as a “load-carrier” structure, for carrying optional equipment, it being possible for said load-carrier structure to be the fuselage of the aircraft or a sponson, for example. The aircraft can then be provided with a removable fastener device for removably fastening an external load, which fastener device comprises attachment means and fastener means for fastening the attachment means under the load-carrier structure.
By way of example, the attachment means may be attachment means of the release hook type, that may be mounted to swivel or not to swivel and that is fastened to the load-carrier structure of the rotorcraft by fastener means. A sling is then attached to the release hook in order to enable it to carry heavy external loads.
The fastener means for fastening such a release hook may comprise:
first means of the universal joint type having two mutually orthogonal pivot axes and referred to as a “sling-ring”;
second means sometimes referred as a “swing”, said second means comprising a frame suspended from the load-carrier structure, e.g. by four suspension cables;
third means implementing a beam to which the equipment is fastened, the beam generally being fastened at two points to the load-carrier structure; and
fourth means implementing a boom fastened to the main power transmission gearbox of the rotorcraft, an equipment being hinged to said boom.
In addition, since the attachment means project from the load-carrier structure, it is appropriate to provide protection in the event of a crash, in particular so as to avoid the removable device and rotably the attachment means damaging the load-carrier structure.
In addition, it can be understood that, in flight, the fastener means and the attachment means together generate aerodynamic drag tending to be detrimental to the speed of the aircraft or to the in-flight fuel consumption of said aircraft. Such disruptive aerodynamic drag is even more of a hindrance while no external load is being carried by said attachment means.
The state of the art includes, in particular Document U.S. Pat. No. 5,850,991, Document U.S. Pat. No. 4,138,078, Document GB 890 178, and Document FR 1 379 420.
Document U.S. Pat. No. 5,850,991 presents a removable device comprising attachment means and fastener means for fastening the equipment, namely respectively a release hook fastened to a beam via a hinge.
The beam is hinged inside a box in order to enable the removable device to be masked inside said box. In a deployed first position, the release hook makes it possible to secure a load. Conversely, in a pivoted second position, the device is contained entirely within the box so that it does not project from the load-carrier structure of the aircraft while being held by dedicated means.
Document U.S. Pat. No. 4,138,078 presents guide means for guiding a release hook carrying a load.
Document GB 890 178 shows a release hook fastened under an aircraft by bars hinged to a load-carrier structure.
Document FR 1 379 420 presents a set of fastenings, each one of which can be lowered or raised independently.
Document U.S. Pat. No. 3,044,818, and Document U.S. Pat. No. 5,499,785 are also known.